Calcium chloride (\(\text{CaCl}_2\)) is definitively not flammable. This odorless, white, crystalline solid is classified as non-combustible. As an ionic compound (a type of salt), its stability and inability to burn are tied directly to its chemical structure, making it a safe material under normal fire conditions.
The Chemistry of Non-Flammability
Calcium chloride’s non-flammable nature stems from its fundamental chemical composition as an ionic salt. Flammability requires a substance to react rapidly with oxygen, a process known as combustion. This reaction involves a fuel source that has not yet reached its highest oxidation state.
The compound \(\text{CaCl}_2\) is already a reaction product formed from calcium and chlorine. The calcium atom has transferred electrons to the chlorine atoms, creating stable ions (\(\text{Ca}^{2+}\) and \(\text{Cl}^{-}\)) held together by strong ionic bonds. This means the compound is already in a fully oxidized state.
Because the calcium is already oxidized, it cannot serve as the fuel source needed to sustain a fire. The substance lacks the chemical energy and structure to combine further with oxygen, preventing it from igniting or burning.
Behavior Under Extreme Heat
Although calcium chloride will not ignite, it reacts to intense heat without contributing to a fire. The anhydrous (water-free) form has a high melting point, typically around 772°C (1422°F). This temperature is significantly higher than the ignition points of most common flammable materials.
When exposed to fire, the solid material will first melt, transforming into a stable molten salt. This molten form does not participate in the combustion process of nearby substances. The boiling point is even higher, listed around 1935°C, meaning extreme conditions are required to vaporize the salt.
If heated to the point of decomposition, it releases toxic and corrosive fumes, specifically chlorine and hydrogen chloride gas. While dangerous, this decomposition reaction does not involve burning and will not fuel the existing fire. Firefighters treat the surrounding fire, as the calcium chloride itself remains non-combustible.
Common Applications and Handling Safety
The chemical stability and non-combustible nature of calcium chloride make it suitable for various applications, including some related to fire safety. It is sometimes included as an additive in fire extinguishers or in fire suppression mixtures. Its primary use, however, is as a de-icing agent on roads, where it melts ice down to temperatures as low as \(-32^\circ\text{C}\) (\(-25^\circ\text{F}\)).
Despite its fire-safe properties, calcium chloride presents significant handling hazards due to its hygroscopic nature. The solid is extremely effective at attracting and absorbing moisture from the air. When it dissolves in water, the process is exothermic, meaning it releases a large amount of heat.
If the solid contacts moist skin, eyes, or mucous membranes, it can cause severe irritation and burns by rapidly drawing out water. Ingestion of the solid or concentrated solutions can cause burns in the mouth and esophagus due to this exothermic reaction and its corrosive properties. Handling requires protective equipment, such as safety glasses and gloves, to prevent direct contact.